Process and apparatus for stripping solids from bituminous sand



Sept. 6, 1966 L. CLARK PnooEss AND APPARATUS Fon STRIPPING somns FROM BITUMINOUS SAND Filed May .'5, 1963 4 Sheets-Sheet 1 rl I l l AWll l l i lvm. l lm OTLWHHMIUVII u KMUQIIIIMW R o T N E v m LNCOLN CLARK ATTORNEY Sept. G, 1966 l L, CLARK PnocEss Aun APPARATUS Foa STRIPPING soLIDs mom BITUMINous SAND 4 Sheets-Sheet 2 Filed May 3, 1963 -i-g-Tm v q. T

INVENTOR LINCOLN CLARK ATTORNEY Sep. w L. CLARK PROCESS AND APPARATUS FOR STRIPPING SOLIDS FROM BITUMINOUS SAND 4 Sheets-Sheet 5 Filed May 3, 1963 SAND SLURRY INVENTOR L l N C OLN C L ARK ATTORNEY Set. 6, L. CLARK 3,271,293

' PROCESS AND APPARATUS FOR STRIPPING SOLIDS mou mummous sANn Filed May 3, 1965 4 Sheets-Sheet 4,

SAND SL URRY FROT ATTORNEY 3,271,293 PROCESS AND APPARATUS FOR STRIPPING SOLIDS FROM BITUMINOUS SAND Lincoln Clark, Newport Beach, Calif., assignor, by direct and mesne assignments, of thirty percent to Cities Service Athabasca, Inc., Edmonton, Alberta, Canada, a cox'- poration of Delaware, thirty percent to Imperial Oil Limited, a corporation of Canada, thirty percent to Atlantic Richfield Company, a corporation of Pennsylvania, and ten percent to Royalite Oil Company Limited, a corporation of Canada Filed May 3, 1963, Ser. No. 277,922 9 Claims. (Cl. 208-11) This invention 'relates to a process and apparatus for the recovery of bitumen from bituminous sand by passing a flotation gas through a bituminous sand slurry. More particularly this invention relates to an improved flotation process and apparatus for the effective use of a flotation gas in'minimizing contamination of ,bitumen rich froth from sand'and fines in a bituminous sand slurry.

Large deposits of bituminous sand are found in various localities throughout the world. The term bituminous sand is used herein to include those materials commonly referred to as oil sand, tar sand and the like. One of the most extensive deposits of bituminous sand occurs, for instance, in the Athabasca district of the Province of Alberta, Canada.

`Typically the composition of these sands con-tain, by weight: from about v6% to about 20% of oil; from about 1% to about 10% of water; and `from about 70% to about 90% of inorganic solids. The specific gravity of the bitumen varies from about 1.0 to abou-t 1.05. (The specific gravity of the bitumen as well as all other values of specific gravity given herein are taken at 60 F.). The major portion, by weight of the inorganic solids is fine grain quartz sand having a particle size greater than about 45 microns and less than 2,000 microns. The remaining inorganic solid matter has a particle size of less than 45 microns and is referred to as fines. The lines contain clay and silt including some very small particles of sand. The lines content typically varies from about 10% to about 30% by weight of the solid inorganic content of bituminous sand. The Vtrue specific gravity of the sand is about 2.65 whereas that of the fines is about 2.7. However, the composition of bituminous sand can vary from the above mentioned ranges and this is not too uncommon. Also, in mining the bituminous sand, clay which is found in layers of varying thickness in such sand areas, may be admixed with the bitumen, thus increasing the inorganic solids content and particularly the fines content of the material to be processed.

Various methods have been proposed for separating bitumen from bituminous sand. .T he two best known methods are often referred to as the hot water method and the cold water method. In the former the bituminous sand is jetted with steam or hot water and mulled with a small proportion of water at about 180 F., and the pulp is then dropped into a turbulent stream of circulating water and carried through a separa-tion cell maintained at an elevated temperature such as that of about 175 F., wherein the oil rises to the top as a froth rich in bitumen which is drawn off.

The so called cold water method does not involve heating the bituminous sand other than whatever hea-t ing might be required to conduct the operation at a temperature of from about 73 F. to 8l F. The process involves mixing the bituminous sand withwater, soda ash and an organic solvent for the bitumen such as kerosene. The mixture is then permitted to settle at a temperature within about 73 F. to 81 F. A mixture of 3,27l,293' Patented Sept. 6, i966 water and bitumen dissolved in the organic solvent rises to the top of the settling zone where it is recovered.

Many of the prior art methods including the hot water method and the cold water method use a gas, usually air, which is passed into the lower portions of a column of water in a flotation tank in order to float or assist flotation of the bitumen as a froth or foam.

A disadvantage of prior art flotation methods and apparatus is that the flotation gas forms bubbles which gradually increase in size and velocity as they come to the surface of the liquid in the llotation tank; and in rising, the gas bubbles break through the top of the water in the tank or through a layer of the bituminous froth which collects above the water. This contaminates the froth since lines are pulled or sucked into the froth layer; also, agitation of the froth by the rising gas bubbles causes additional water and fines to become entrained with the froth, particularly since a fairly high concentration of lines collect at the water-froth interface.

It is an object of this invention to provide an improved process and apparatus for producing froth in bituminous sand slurries which can be used with either the hot or cold water methods described hereinabove.

It is a further object of this invention to provide a process and apparatus for producing froth in bituminous sand slurries wherein the froth is not unnecessary contaminated with fines and sand.

It is a further object of this invent-ion to provide a process and apparatus for entrapping froth formed with a flotation gas and excess flotation gas; i.e., gas which is not a part of the froth structure, below the surface of a layer of bituminous froth in a flotation tank, also referred to herein as a stripper, containing a bituminous sand slurry, and passing the rising froth and excess gas out of contact with and above the water-froth interface in said tank.

These and other aspects of the invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a side elevation of a flotation tank and gas trap of this invention;

FIG. 2 is a partially cut away front view of the flotation tank and gas trap of FIG. 1;

FIG. 3 is a plan view of the flotation tank and gas trap of FIGS. 1 and 2;

FIG. 4 is an isometric view of a modified flotation tank and gas trap;

FIG. 5 is an elevation of the flotation tank and gas trap of FIG. 4;

FIG. 6 is a plan view of the flotation tank and gas trap of FIGS. 4 and 5; and

FIG. 7 is a modified gas trap discharge means.

In the process of this invention a slurry of bituminous sand is introduced into the upper portion of a flotation tank containing a column of water. The portion of the flotation tank, or stripper into which the slurry is introduced has a decreasing internal cross-section below the surface of the column of water; e.g., it is shaped as a trough, funnel or inverted cone as will be more fully described hereinafter. The slurry which is fed into the stripper can be formed by conventional means; e.g., by adding water or an organic solvent for the bitumen to the bituminous sand and agitating the mixture, preferably in contact with air. When water is used to form the slurry, from about 12.0% to about 65.0% and preferably from about 40.0% to about 55.0% of the bituminous sand slurry is composed of water. When an organic solvent is added, such as for instance kerosene, from about 0.5% to about 20.0% by weight of the slurry is composed of the organic solvent. The slurry is mixed and agitated at temperatures varying from about 70 F. to about 210 F. and preferably from about 110 F. to about 180 F. Due to the temperature of the slurry or the mixing and agitating of the slurry in contact with air, the slurry forms a froth upon entering the column of water in the stripper which is within the temperature ranges given hereinabove for the slurry. The froth rises within the column of Water in the stripper to form a layer over the water. Preferably the process is continuous and the slurry is introduced below the top surface of the water in the stripper so as not to unduly agitate the bituminous froth.

The sand content of the bituminous sand slurry proceeds by gravity and to a varying extent by the velocity of the incoming slurry, to pass downwardly in the stripper. Also, fines and particles of bitumen which have not formed froth pass downwardly in the stripper. As mentioned hereinbefore, the internal diameter of the zone of column of water receiving the slurry has a narrower cross section at its lower portions as compared to its upper portions; e.g., this column of water has a vertical cross section resembling a funnel, trough or inverted cone. The heavy material in the slurry passes downwardly within the restricted area. At the lower portions of the restricted area, or therebelow are means for introducing a flotation gas upwardly into the column of water. Optionally, in much the same location means can be provided for introducing hot water upwardly into 'the standing column of w-ater. Thus, as the sand, particles of bitumen and fines settle towards the bottom of the stripper they are contacted with the rising gas or rising gas and hot water. The velocity of these rising uids is insucient to prevent the heavy grains of sand from settling. The sand continues its downward movement to the bottom of the stripper. However, the particles of bitumen and some of the fines are carried upwardly. The bitumen particles attach themselves or join the liquid interphase about the gas and are carried upwardly with gas as froth.

The otation gas can be admitted into the stripper by various means such yas jets, spargers, diffuser, a combination of these means or simply through a pipe having small openings which runs across a lower portion of the funnellike zone or below the throat of the funnel-like zone. The amount of air admitted into the stripper can vary up to about 400 standard cubic feet per hour per square foot (s.c.f./hr./ft.2) of water through a transverse cross section of the column of water which is -being contacted with air and preferably from about 150 to about 360 s.c.f./ hr./ft.2. The pressure of the flotation gas can vary over wide limits such as that of about 20 p.s.i.g. to about 40 p.s.i.g. depending upon back pressure. -A gas trap is provided at the upper portion of the stripper in axial alignment with the rising gas. The bottom of the trap is below the surface of the column of water in the stripper. Some of the fines and froth are propelled into this trap which can take various forms as will be more fully described hereinafter. The trap has riders extending above the froth level on the column of water for permitting excess gas to escape and for permitting the froth which is formed'by the rising fluids to join the main layer of froth in the stripper or to be separately recovered. The gas trap displaces a minor portion of the column of water at its surface. Preferably only the risers extend through the surface of the water which will have a layer of froth. The sand settles to the bottom of the stripper where it can be removed. Optionally as shown in FIGS. 1-3, a separate zone in the stripper receives the sand. Means are provided for removing the froth and for removing excess water from the stripper. The excess water in the stripper can be discarded or can be passed to a secondary recovery unit for stripping of additional bitumen or for removing both bitumens and fines.

Referring to the drawings wherein identical numerals refer to identical parts, and particularly FIGS. 1 to 3, l0 is a bituminous slurry intake pipe having an opening 12 for admitting the slurry into stripper 14 below the surface of a column of water 16. Below and in axial alignment with opening 12 is a horizontal battle 18 on which the slurry impinges. Horizontal baille 18 can be attached to intake pipe 10 by means of bracket assembly 20. A bituminous froth 22 floats up `above the surface 24 of the water. Below horizontal bale 18 is gas trap 26. The gas trap has downwardly slanted side panels 28 and 30 and vertical end panels 32 and 34. Thus the trap is in the form of a longitudinally extended triangular funnel having its apex communicating with vertical gas risers 4Z and 44, which extend above the layer of foam 22 and terminate in caps 48. Above froth 22 are openings 46 venting the risers to the atmosphere and providing means for the froth from the trap to join the remaining froth in the stripper. The `air trap can be attached to the ends 52 and 54 of the stripper by means of bolts or braces 50. The incoming slurry pipe 10 can be held in place and attached to the risers 42 and 44 by means of brackets 56.

The sides 58 and 60 and ends 52 and 54 of the stripper are substantially vertical except at lower portions 62 of the stripper where the sides covergc inwardly forming an inverted conical bottom. Downwardly inclined plates 64 and 66 which have substantially vertical lower portions 68 and 70 are attached adjacent their top edges 72 and 74 to the sides of the stripper 58 and 60 respectively. The ends ofthe downwardly inclined plates, 64 and 66 throughout their entire length including lower portions 68 and 70 are attached to ends 52 and 54 of the stripper. These plates in cooperation with ends 52 and 54 of the stripper form a longitudinally extended funnel or trough 76 in the stripper. Except for top edges 72 and 74 the downwardly inclined plates are spaced from sides 58 and 60 of the stripper.

The slurry entering the stripper is mixed with water and the heavy particles such as sand, particles of bitumen and fines move downwardly in trough 76 toward trough throat 78 and throat opening 80. Horizontal pipes 82 and 83 run through the throat.

Pipe 82 has openings 84 for admitting a flotation gas into the throat 78 of the trough 76; whereas pipe 83 has openings 86 for admitting water therein.

The sand passes downwardly through the trough throat and the sand 87 settles in the bottom 88 of the stripper. An Opening 57 is provided in the bottom of the stripper for the discharge of sand. Gas or a combination of gas and hot water is released through pipe openings 84 and 86 and travels upwardly to the trap. The gas in its upward movement, which can be aided by hot water, lloats the bitumen upwardly. ln addition to bitumen some nes are also propelled upwardly. The rising gas including bitumen (which may now be in the form of a froth) and fines are collected within the gas trap 26. The gas, including bituminous froth and nes in the trap are propelled upwardly into the risers where they are discharged through openings 46. The froth and fines fall downwardly from openings 46 onto the layer of froth in the stripper whilel excess gas moves upwardy into the atmosphere. The lower portion of the stripper 14 has upwardly sloping baffles 90 and 92. These baflles are attached to the front and re-ar sides 58 nd 60 of the stripper and extendto a point above the sides of the opening in the throat in spaced relation to the funnel thus leaving an opening to lateral compartments 94 and 96 formed above baffles 90 and 92. Excess water flows out of the stripper through openings 98, 99 and 100 in egress pipes 102, 103 land 104. The lateral compartments 94 and 96 have secondary baffles 106. Baies 90, 92 and 106 extend across the stripper and are attached to sides 52 and 54. Water from opening in throat 78 ows toward discharge openings 98 between the openings 108 and 110 defined by baiiies and 92 with throat 78. Some of the sand in the wa'ter impinges on these bailles and falls toward bottom 88. Water flowing past openings 108 and 110 impinges against baffles 106 where additional sand 112 is separated and falls in troughs 114 and 116. Conduit means 113 and 120 remove sand from the troughs 114 and 116. The water then flows out of pipe 102 into a conduit 122. Optionally pipe 103 from lateral compartment 104 also flows in conduit 1,22. Frictional, vertically adjustable cylinder 124 is provided at the top of pipe 102 for ladjusting the level ofthe water in the stripper.

The top of the stripper has arcuate plate 126 leading into a trough 128. Above arcuate plate 126 are means such as a paddle Wheel, shown in dotted lines at 129, for

skimming the froth ott the top of the tank. This can best be seen in FIGURE 2.

FIGURES 4, 5, and 6 show a anodied stripper 130 'whose mode of operation is much the same as stripper 14. Irl-stripper 130 the lateral compartments 94 and 96 of the previous stripper are missing. Instead the stripper funnels down to a substantially cylindrical tube 132 having inlets 134 at its lower portion for admitting air and water. The bituminous sand slurry enters the stripper through inrl'et pipe 136 which extends to below the froth and water interface 138. The slurry forms a froth 22 at the top of the water layer 16. The heavy particles in the slurry flow downwardly over the top and sides of gas trap 140. Trap 140 is in the shape of a cone and has a gas riser 142 which extends above the top of the froth. The riser has an opening 144 at its top from which excess gas and froth are discharged. The riser opening 144 has a protective cap 146 in spaced relation to the opening 144. The gas trap assembly can be held in place through bracket 146 which is attached to the stripper. Optionally a baffle 148 partly blocking opening 150 can be placed adjacent the trap and attached to the shell of the stripper. As in FIG. 1 the stripper has downwardly sloping sides 145 forming a funnel. The heavier particles in the slurry move downwardly into the throat 132 of the funnel where they are contacted by rising gas or gas and water from spargers, jets or ditl'users 152. The upwardly moving gas causes the bitumen to rise and form a froth. Some of the fines also rise with the gas and the rising material is caught within trap 140, carried through riser 142 and out of opening 144. Excess gas from riser opening 144 is vented to the atmosphere whereas the foam and fines drop down over the foam layer 22 in the stripper. The sand collects at the bottom 154 of the stripper and is removed from the stripper by star valve 156. The foam at the top of the stripper flows over the sides 158 and 161 of the stripper or is skimmed ot by paddles 160'and the froth flows into conduits 162 where it can be passed to further upgrading or recovered in container 163. Paddles 160 are journaled into the top of the stripper through shafts 164 and have means such as pulleys 166 and belt 168 for imparting rotation to the paddles. The water level in the stripper is maintained by means of openings 170 which connects by conduit means 172 with opening 150 in the upper portion of the stripper and opening 174 in the throat of the stripper. The upper portion of conduit 172 has a vertical member 176 which has means for vertical adjustment and controlling the water level through opening 170. The etll'uent'water flows out through piping 178. Valves 180 and 182 can be inserted in the piping for controlling the ettl uent water flow.

FIG. 7 shows a modification of the gas and foam egress meansl from the risers in FIGS. 1-6. In FIG. 7, upper part of riser 184 has' opening 186 above the foam level. A cylindrical tube 188 which is open at both its bottom and its top end is secured concentrically on riser 184 with bracket 189. In this embodiment the foam and lines raised by thegas are discharged through openings 186 and the excess gas rises upwardly through the cylindrical tube to vent into the atmosphere. The foam and fines settle downwardly and pass through the bottom opening of the cylindrical tube 188. The foam joins the layer of foam in the stripper whereas the fines continue their downward movement in the stripper. This embodiment further minimizes the mixture of tines with the layer of foam in the stripper.

The invention will be more readily understood from the following detailed description of a continuous process wherein quantities are given on a per hour basis, unless otherwise indicated, in conjunction with the drawings. The below described example can be practiced with the apparatus of either' FIGS. 1-3 or FIGS. 4-6. For the sake of convenience the process of the below example will bc described with reference to the apparatus of FIGS. l-3.

EXAMPLE I A-n aqueous slurry of Alberta bituminous sand is passed into the top of stripper 14 by means of inlet pipe 10 below the surface 24 of a column of water 16. The bituminous sand prior to slurrying contains 2,326 pounds of bitumen, 1,557 lbs. of water and 16,000 lbs. of solid which on -a weight basis is 11.7% bitumen, 5.3% water and 83.0% solids. A small part of the bitumen (50 lbs.) and solids lbs.) is lost by mixing in -a tumbler having an end opening for discharging stone which is mined with the bituminous sand. Sufficient water is added to the bituminous sand in the tumbler and prior to the slurrys entrance in the stripper so that the bituminous sand slurry contains 2,316 lbs. of bitumen, 13,792 lbs. of water and 15,815 lbs. of solids. The slurry from the tumbler is divided into 4 equal streams and enters four strippers such as stripper 14 as mentioned hereinabove. Into the four strippers there is also fed a total of 300 s.c.f./hr. of air per square foot of water column cross area within the throat 78 of the strippers through pipe 82 and openings 84. The -air is fed in at 20 p.s.i.g. and 60 F. The temperature at which the slurry enters the stripping tank is about 180 F. and the water in the stripping tank is maintained at this temperature. In addition to the air there is separately introduced 7,900 lbs. of water through the pipe 83 having openings 86 at a temperature of about 180 F. Froth at about 170 F. is recovered from the top of the stripper 126 by overtiow or skimming with the paddle 129 .and is passed to conduit 128. Ettluent water (15,772 lbs.) is recovered from the strippers through trough 122. The effluent water also contains 446 lbs. of bitumen and 2,080 lbs. of solids which are composed almost entirely of fines. Solids are recovered from the bottom opening 57 of the strippers and lateral compartment openings 118 and 120. The total amount of solids recovered from the stripper is 13,275 lbs. This includes 1,897 lbs. of nes. Additionally 4,500 lbs. of water and lbs. of bitumen are mixed in with the solids. The froth from the stripper contains 1,780 lbs. of bitumen, 1,420 lbs. of Water and 460 lbs. of solids which are composed almost entirely of fines. Thus the froth is composed of 48.7% bitumen, 38.8% water and 12.5% solids. By operating this process without the air trap the solids in the froth can increase from the 12.5% value to upward of 30.0% with a commensurate decrease of the bitumen. Also, the water content of the froth is increased without the use of a trap.

The following example illustrates the importance of a gas trap such as the gas trap 26 described above in connection with FIGS. 1-3 or the gas trap 140 described in connection with FIGS. 4-6 in the recovery of bitumen from bituminous sand in processes of the type described above.

EXAMPLE II For this example bitumen was separated from sand in a stripper similar to the stripper 14 shown in FIGS. l-3 and described above except that for run number 2 the gas trap 26 was removed. The feed to the stripper for these runs was an aqueous slurry prepared by mixing raw bituminous sand with water to form a slurry conrtaining about 22 weight percent water and then agitating with additional water to form a slurry containing about 41 weight percent water. This slurry was then intro duced into the stripper at a constant feed rate while air was added to the stripper at the rate of 300 standard cubic feet of air per hour per square foot of cross-sectional area of the throat 78 and water was added at the aa'raaea Iresults of run No. 1, in which the gas trap 26 was used,

with the results of run No. 2, in which the gas trap was not used revealed the following:

Table .l

Bitumen recovered in Solids iu recovered bllroth from stripper turnen (wt. percent) (wt. percent based on bitumen ln raw bituminous sand) ltun No.

1 (gas trap) 6r 7 10. 7 2 (no gas trap) 19. 2

The above data shows that the use of a gas trap results in greater recovery of bitumen containing lower concentrations of solids than is obtained without such a trap.

The hereinabove description is directed to illustrate rembodiments of apparatus and process for practicing the invention, and it will be understood that various modifications may be made without departing from the scope of the invention.

The flotation gas is preferably air, however, other flotation gases such as methane, or nitrogen can also be employed.

It should be pointed out that the flotation apparatus and process described above may also be employed to carry out other `separations involving flotation. Illustratively where iron sulfide is to be converted `to iron oxide, and the iron sulfide is in the form of a line suspension ol' solid material and water, such a suspension may be employed as a feed liquid and air may be employed as a flotation agent in the apparatus of this invention. The iron sulfide is then converted to iron oxide and free sulfur inthe flotation operation, and the sulfur is floated to the top of the tank and skimmed olf in much the same manner as described for the bitumen.

I claim:

1. A process for separating bitumen from bituminous sand slurry which comprises passing a bituminous sand slurry into a body of water, guiding material in said Ibituminous sand including `bitumen heavier than water downwardly through --a column of water having a decreased cross-section, passing a flotation gas upwardly through said column within the area of decreased cross-section below the slurry entrance, said gas rising and contacting the downwardly flowing bitumen and floating a portion thereof upwardly, entrapping the rising gas and bitumen in a confined area below the top of the water column, conducting the entrapped gas and bitumen upwardly above above and out of contact with the water in said column and permitting the gas to vent thereabove.

2. The process of claim l when the temperature of the slurry varies from about 110 F. to about 200 F.

3. The process of claim l when the 'bitumen is co1- lected as a froth above the column of water.

4. A process for decreasing'contamination of bitumen rich froth from bituminous sand which comprises:

(a) introducing an aqueous slurry of bituminous sand below the top of a body of water at a temperature of from about 110 F. to about 200 F.;

(b) permitting material including particles of bitumen in said slurry having a specific gravity greater than that of water to pass downwardly lby gravity in said body of water;

(c) funneling said downwardly passing material into a column of water having a decreased cross section as compared tothe body of water above said column of water;

(d) passing rising bubbles of air into said column of water land contacting the downwardly moving particles with air;

(e) floating bitumen upwardly with the rising air;

(f) entrapping a mixture of upwardly rising bitumen and air above said column of water of reduced cross sectional area and ou-t of contact with the surface of the body of water;

(g) funneling the entrapped mixture of bitumen and air upwardly through a passage having a decreased cross section as compared to the area entrapping the rising bitumen and air;

(h) said mixture of bitumen and air being conducted in said passage above the surface of said body of Water;

(i) and finally venting excess air into the atmosphere and discharging the bitumen as a froth above the surf-ace of water.

5. The process of claim l wherein the froth is passed under the surface of the water after venting excess air.

6. Flotation apparatus comprising an opstanding tank having a funnel-shaped vertical zone including a top wider than its stem, means adjacent the top of said funnel for recovering bituminous froth, means below said bituminous froth recovery means for introducing a slurry, an inverted funnel-shaped air trap within the wide portion of said funnel and in axial alignment with the funnel stem, the air trap being below the froth recovery means and having an air riser extending above the froth recovery means and means to admit air within lower portions of the funnel stem zone.

7. A flotation apparatus suitable for recovering bituminous froth from bituminous sand comprising, in combination, a vertical vessel having a funnel-shaped vertical zone including a top wider than its stem, means adjacent the top of said zone for recovering froth, means below the froth recovery means for removing water from the funnel-shaped zone, means below the water egress means for admitting a bituminous slurry into the top of said funnel, means for admitting air into the funnel stem, means for recovering sand from the bottom of the vessel, an inverted funnel-shaped air trap above the stem of the funnel shaped zone and in axial alignment therewith, said trap having inclined sides spaced from the vessel and the major portion thereof extending below the froth recovery means and below the slurry intake means, and a conduit rising from the top of the inverted funnel upwardly and having an opening above the Water egress means.

8. Flotation apparatus comprising an upstanding vessel having an interior vertical zone, the upper portion of said zone having a wide mouth and the lower portion thereof a narrow throat, a column of water in said vertical zone, a layer of froth floating on said column of water, means for admitting a slurry into said zone below the t-op of the column of water, means for removing a froth above the column of water, means for removing sand below the throat, means for admitting air into said throat, means for entrapping air and froth above said zone and below the surface of the water, said entrapping means displacing a minor portion of the area at the surface of the water, and riser means extending above the air entrapping means and having Ian opening above the layer of froth, said riser means having a cross sectional area small in comparison with that of the entrapping means.

9. A process for separating bitumen from bituminous sand which comprises passing a bituminous sand slurry into a body of water, guiding material in said bituminous sand including bitumen heavier than water downwardly through a column of water having a decreased cross section relative to said body of water, passing a flotation gas upwardly through said column of water of decreased cross section below the point of entry of said slurry into said body of water, said gas rising and contacting the downwardly flowing bitumen and floating a portion thereof upwardly, entrapping a mixture of upwardly rising 9 1 0 bitumen and air at a point in said body of water above 2,297,586 9/ 1942 Steffensen 209-170 said column of water of reduced cross section and below 2,924,566 2/ 1960 Vaell et al. 208-11 the surface of the body of water, conducting the entrapped 2,965,557 12/1960 Price 208-11 gas and bitumen upwardly through a pass-age having a 3,152,979 10/ 1964 Bichard et al. 208-11 decreased cross sectional area as compared to the area in 5 which the air and bitumen is entrapped to a point above FOREIGN PATENTS the surface of said body of water and permitting the gas 448,231 5/1948 Canada t0 Vent there above- DANIEL E. WYMAN, Primary Examinar.

10 ALPHONSO D. SULLIVAN, Examiner.

H. LEVINE, P. E. KONOPKA, Assislant Examiners.

References Cited by the Examiner UNITED STATES PATENTS 1,497,607 6/1924 Streppel 208-11 1,732,893 10/1929 H unt 209-170 

1. A PROCESS FOR SEPARATING BITUMEN FROM BITUMINOUS SAND SLURRY WHICH COMPRISES PASSING A BITUMINOUS SAND SLURRY INTO A BODY OF WATER, GUIDING MATERIAL IN SAID BITUMINOUS SAND INCLUDING BITUMEN HEAVIER THAN WATER DOWNWARDLY THROUGH A COLUMN OF WATER HAVING A DECREASED CROSS-SECTION, PASSING A FLOTATION GAS UPWARDLY THROUGH SAID COLUMN WITHIN THE AREA OF DECREASED CROSS-SECTION BELOW THE SLURRY ENTRANCE, SAID GAS RISING AND CONTACTING THE DOWNWARDLY FLOWING BITUMEN AND FLOATING A PORTION THEREOF UPWARDLY, ENTRAPPING THE RISING GAS AND BITUMEN IN A CONFINED AREA BELOW THE TOP OF THE WATER COLUMN, CONDUCTING THE EENTRAPPED GAS AND BITUMEN UPWARDLY ABOVE AND OUT OF CONTAACT WITH THE WATER IN SAID COLUMN AND PERMITTING THE GAS TO VENT THEREABOVE. 